'use strict';

const canvas = document.getElementsByTagName('canvas')[0];
resizeCanvas();

let config = {
    SIM_RESOLUTION: 128,
    DYE_RESOLUTION: 1024,
    CAPTURE_RESOLUTION: 512,
    DENSITY_DISSIPATION: 2,
    VELOCITY_DISSIPATION: 2,
    PRESSURE: 0.8,
    PRESSURE_ITERATIONS: 20,
    CURL: 30,
    SPLAT_RADIUS: 0.25,
    SPLAT_FORCE: 6000,
    SHADING: true,
    COLORFUL: true,
    COLOR_UPDATE_SPEED: 10,
    PAUSED: false,
    BACK_COLOR: { r: 0, g: 0, b: 0 },
    TRANSPARENT: false,
    BLOOM: true,
    BLOOM_ITERATIONS: 8,
    BLOOM_RESOLUTION: 256,
    BLOOM_INTENSITY: 0.8,
    BLOOM_THRESHOLD: 0.6,
    BLOOM_SOFT_KNEE: 0.7
}

function pointerPrototype() {
    this.id = -1;
    this.texcoordX = 0;
    this.texcoordY = 0;
    this.prevTexcoordX = 0;
    this.prevTexcoordY = 0;
    this.deltaX = 0;
    this.deltaY = 0;
    this.down = false;
    this.moved = false;
    this.color = [30, 0, 300];
}

let pointers = [];
let splatStack = [];
let bloomFramebuffers = [];
pointers.push(new pointerPrototype());

const { gl, ext } = getWebGLContext(canvas);

if (isMobile()) {
    config.DYE_RESOLUTION = 512;
}
if (!ext.supportLinearFiltering) {
    config.DYE_RESOLUTION = 512;
    config.SHADING = false;
    config.BLOOM = false;
}

// startGUI();

function getWebGLContext(canvas) {
    const params = { alpha: true, depth: false, stencil: false, antialias: false, preserveDrawingBuffer: false };

    let gl = canvas.getContext('webgl2', params);
    const isWebGL2 = !!gl;
    if (!isWebGL2)
        gl = canvas.getContext('webgl', params) || canvas.getContext('experimental-webgl', params);

    let halfFloat;
    let supportLinearFiltering;
    if (isWebGL2) {
        gl.getExtension('EXT_color_buffer_float');
        supportLinearFiltering = gl.getExtension('OES_texture_float_linear');
    } else {
        halfFloat = gl.getExtension('OES_texture_half_float');
        supportLinearFiltering = gl.getExtension('OES_texture_half_float_linear');
    }

    gl.clearColor(0.0, 0.0, 0.0, 1.0);

    const halfFloatTexType = isWebGL2 ? gl.HALF_FLOAT : halfFloat.HALF_FLOAT_OES;
    let formatRGBA;
    let formatRG;
    let formatR;

    if (isWebGL2) {
        formatRGBA = getSupportedFormat(gl, gl.RGBA16F, gl.RGBA, halfFloatTexType);
        formatRG = getSupportedFormat(gl, gl.RG16F, gl.RG, halfFloatTexType);
        formatR = getSupportedFormat(gl, gl.R16F, gl.RED, halfFloatTexType);
    }
    else {
        formatRGBA = getSupportedFormat(gl, gl.RGBA, gl.RGBA, halfFloatTexType);
        formatRG = getSupportedFormat(gl, gl.RGBA, gl.RGBA, halfFloatTexType);
        formatR = getSupportedFormat(gl, gl.RGBA, gl.RGBA, halfFloatTexType);
    }

    //ga('send', 'event', isWebGL2 ? 'webgl2' : 'webgl', formatRGBA == null ? 'not supported' : 'supported');

    return {
        gl,
        ext: {
            formatRGBA,
            formatRG,
            formatR,
            halfFloatTexType,
            supportLinearFiltering
        }
    };
}

function getSupportedFormat(gl, internalFormat, format, type) {
    if (!supportRenderTextureFormat(gl, internalFormat, format, type)) {
        switch (internalFormat) {
            case gl.R16F:
                return getSupportedFormat(gl, gl.RG16F, gl.RG, type);
            case gl.RG16F:
                return getSupportedFormat(gl, gl.RGBA16F, gl.RGBA, type);
            default:
                return null;
        }
    }

    return {
        internalFormat,
        format
    }
}

function supportRenderTextureFormat(gl, internalFormat, format, type) {
    let texture = gl.createTexture();
    gl.bindTexture(gl.TEXTURE_2D, texture);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.NEAREST);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.NEAREST);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
    gl.texImage2D(gl.TEXTURE_2D, 0, internalFormat, 4, 4, 0, format, type, null);

    let fbo = gl.createFramebuffer();
    gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
    gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);

    const status = gl.checkFramebufferStatus(gl.FRAMEBUFFER);
    return status == gl.FRAMEBUFFER_COMPLETE;
}

function isMobile() {
    return /Mobi|Android/i.test(navigator.userAgent);
}

function captureScreenshot() {
    let res = getResolution(config.CAPTURE_RESOLUTION);
    let target = createFBO(res.width, res.height, ext.formatRGBA.internalFormat, ext.formatRGBA.format, ext.halfFloatTexType, gl.NEAREST);
    render(target);

    let texture = framebufferToTexture(target);
    texture = normalizeTexture(texture, target.width, target.height);

    let captureCanvas = textureToCanvas(texture, target.width, target.height);
    let datauri = captureCanvas.toDataURL();
    downloadURI('fluid.png', datauri);
    URL.revokeObjectURL(datauri);
}

function framebufferToTexture(target) {
    gl.bindFramebuffer(gl.FRAMEBUFFER, target.fbo);
    let length = target.width * target.height * 4;
    let texture = new Float32Array(length);
    gl.readPixels(0, 0, target.width, target.height, gl.RGBA, gl.FLOAT, texture);
    return texture;
}

function normalizeTexture(texture, width, height) {
    let result = new Uint8Array(texture.length);
    let id = 0;
    for (let i = height - 1; i >= 0; i--) {
        for (let j = 0; j < width; j++) {
            let nid = i * width * 4 + j * 4;
            result[nid + 0] = clamp01(texture[id + 0]) * 255;
            result[nid + 1] = clamp01(texture[id + 1]) * 255;
            result[nid + 2] = clamp01(texture[id + 2]) * 255;
            result[nid + 3] = clamp01(texture[id + 3]) * 255;
            id += 4;
        }
    }
    return result;
}

function clamp01(input) {
    return Math.min(Math.max(input, 0), 1);
}

function textureToCanvas(texture, width, height) {
    let captureCanvas = document.createElement('canvas');
    let ctx = captureCanvas.getContext('2d');
    captureCanvas.width = width;
    captureCanvas.height = height;

    let imageData = ctx.createImageData(width, height);
    imageData.data.set(texture);
    ctx.putImageData(imageData, 0, 0);

    return captureCanvas;
}

function downloadURI(filename, uri) {
    let link = document.createElement('a');
    link.download = filename;
    link.href = uri;
    document.body.appendChild(link);
    link.click();
    document.body.removeChild(link);
}

class GLProgram {
    constructor(vertexShader, fragmentShader) {
        this.uniforms = {};
        this.program = gl.createProgram();

        gl.attachShader(this.program, vertexShader);
        gl.attachShader(this.program, fragmentShader);
        gl.linkProgram(this.program);

        if (!gl.getProgramParameter(this.program, gl.LINK_STATUS))
            throw gl.getProgramInfoLog(this.program);

        const uniformCount = gl.getProgramParameter(this.program, gl.ACTIVE_UNIFORMS);
        for (let i = 0; i < uniformCount; i++) {
            const uniformName = gl.getActiveUniform(this.program, i).name;
            this.uniforms[uniformName] = gl.getUniformLocation(this.program, uniformName);
        }
    }

    bind() {
        gl.useProgram(this.program);
    }
}

function compileShader(type, source, keywords) {
    if (keywords != null) {
        let keywordsString = '';
        keywords.forEach(keyword => {
            keywordsString += '#define ' + keyword + '\n';
        });
        source = keywordsString + source;
    }

    const shader = gl.createShader(type);
    gl.shaderSource(shader, source);
    gl.compileShader(shader);

    if (!gl.getShaderParameter(shader, gl.COMPILE_STATUS))
        throw gl.getShaderInfoLog(shader);

    return shader;
};

const baseVertexShader = compileShader(gl.VERTEX_SHADER, `
    precision highp float;
    attribute vec2 aPosition;
    varying vec2 vUv;
    varying vec2 vL;
    varying vec2 vR;
    varying vec2 vT;
    varying vec2 vB;
    uniform vec2 texelSize;
    void main () {
        vUv = aPosition * 0.5 + 0.5;
        vL = vUv - vec2(texelSize.x, 0.0);
        vR = vUv + vec2(texelSize.x, 0.0);
        vT = vUv + vec2(0.0, texelSize.y);
        vB = vUv - vec2(0.0, texelSize.y);
        gl_Position = vec4(aPosition, 0.0, 1.0);
    }
`);

const copyShader = compileShader(gl.FRAGMENT_SHADER, `
    precision mediump float;
    precision mediump sampler2D;
    varying highp vec2 vUv;
    uniform sampler2D uTexture;
    void main () {
        gl_FragColor = texture2D(uTexture, vUv);
    }
`);

const clearShader = compileShader(gl.FRAGMENT_SHADER, `
    precision mediump float;
    precision mediump sampler2D;
    varying highp vec2 vUv;
    uniform sampler2D uTexture;
    uniform float value;
    void main () {
        gl_FragColor = value * texture2D(uTexture, vUv);
    }
`);

const colorShader = compileShader(gl.FRAGMENT_SHADER, `
    precision mediump float;
    uniform vec4 color;
    void main () {
        gl_FragColor = color;
    }
`);

const checkerboardShader = compileShader(gl.FRAGMENT_SHADER, `
    precision highp float;
    precision highp sampler2D;
    varying vec2 vUv;
    uniform sampler2D uTexture;
    uniform float aspectRatio;
    #define SCALE 25.0
    void main () {
        vec2 uv = floor(vUv * SCALE * vec2(aspectRatio, 1.0));
        float v = mod(uv.x + uv.y, 2.0);
        v = v * 0.1 + 0.8;
        gl_FragColor = vec4(vec3(v), 1.0);
    }
`);

const displayShaderSource = `
    precision highp float;
    precision highp sampler2D;
    varying vec2 vUv;
    varying vec2 vL;
    varying vec2 vR;
    varying vec2 vT;
    varying vec2 vB;
    uniform sampler2D uTexture;
    uniform sampler2D uBloom;
    uniform sampler2D uDithering;
    uniform vec2 ditherScale;
    uniform vec2 texelSize;
    vec3 linearToGamma (vec3 color) {
        color = max(color, vec3(0));
        return max(1.055 * pow(color, vec3(0.416666667)) - 0.055, vec3(0));
    }
    void main () {
        vec3 c = texture2D(uTexture, vUv).rgb;
    #ifdef SHADING
        vec3 lc = texture2D(uTexture, vL).rgb;
        vec3 rc = texture2D(uTexture, vR).rgb;
        vec3 tc = texture2D(uTexture, vT).rgb;
        vec3 bc = texture2D(uTexture, vB).rgb;
        float dx = length(rc) - length(lc);
        float dy = length(tc) - length(bc);
        vec3 n = normalize(vec3(dx, dy, length(texelSize)));
        vec3 l = vec3(0.0, 0.0, 1.0);
        float diffuse = clamp(dot(n, l) + 0.7, 0.7, 1.0);
        c *= diffuse;
    #endif
    #ifdef BLOOM
        vec3 bloom = texture2D(uBloom, vUv).rgb;
        float noise = texture2D(uDithering, vUv * ditherScale).r;
        noise = noise * 2.0 - 1.0;
        bloom += noise / 255.0;
        bloom = linearToGamma(bloom);
        c += bloom;
    #endif
        float a = max(c.r, max(c.g, c.b));
        gl_FragColor = vec4(c, a);
    }
`;

const displayShader = compileShader(gl.FRAGMENT_SHADER, displayShaderSource);
const displayBloomShader = compileShader(gl.FRAGMENT_SHADER, displayShaderSource, ['BLOOM']);
const displayShadingShader = compileShader(gl.FRAGMENT_SHADER, displayShaderSource, ['SHADING']);
const displayBloomShadingShader = compileShader(gl.FRAGMENT_SHADER, displayShaderSource, ['BLOOM', 'SHADING']);

const bloomPrefilterShader = compileShader(gl.FRAGMENT_SHADER, `
    precision mediump float;
    precision mediump sampler2D;
    varying vec2 vUv;
    uniform sampler2D uTexture;
    uniform vec3 curve;
    uniform float threshold;
    void main () {
        vec3 c = texture2D(uTexture, vUv).rgb;
        float br = max(c.r, max(c.g, c.b));
        float rq = clamp(br - curve.x, 0.0, curve.y);
        rq = curve.z * rq * rq;
        c *= max(rq, br - threshold) / max(br, 0.0001);
        gl_FragColor = vec4(c, 0.0);
    }
`);

const bloomBlurShader = compileShader(gl.FRAGMENT_SHADER, `
    precision mediump float;
    precision mediump sampler2D;
    varying vec2 vL;
    varying vec2 vR;
    varying vec2 vT;
    varying vec2 vB;
    uniform sampler2D uTexture;
    void main () {
        vec4 sum = vec4(0.0);
        sum += texture2D(uTexture, vL);
        sum += texture2D(uTexture, vR);
        sum += texture2D(uTexture, vT);
        sum += texture2D(uTexture, vB);
        sum *= 0.25;
        gl_FragColor = sum;
    }
`);

const bloomFinalShader = compileShader(gl.FRAGMENT_SHADER, `
    precision mediump float;
    precision mediump sampler2D;
    varying vec2 vL;
    varying vec2 vR;
    varying vec2 vT;
    varying vec2 vB;
    uniform sampler2D uTexture;
    uniform float intensity;
    void main () {
        vec4 sum = vec4(0.0);
        sum += texture2D(uTexture, vL);
        sum += texture2D(uTexture, vR);
        sum += texture2D(uTexture, vT);
        sum += texture2D(uTexture, vB);
        sum *= 0.25;
        gl_FragColor = sum * intensity;
    }
`);

const splatShader = compileShader(gl.FRAGMENT_SHADER, `
    precision highp float;
    precision highp sampler2D;
    varying vec2 vUv;
    uniform sampler2D uTarget;
    uniform float aspectRatio;
    uniform vec3 color;
    uniform vec2 point;
    uniform float radius;
    void main () {
        vec2 p = vUv - point.xy;
        p.x *= aspectRatio;
        vec3 splat = exp(-dot(p, p) / radius) * color;
        vec3 base = texture2D(uTarget, vUv).xyz;
        gl_FragColor = vec4(base + splat, 1.0);
    }
`);

const advectionShader = compileShader(gl.FRAGMENT_SHADER, `
    precision highp float;
    precision highp sampler2D;
    varying vec2 vUv;
    uniform sampler2D uVelocity;
    uniform sampler2D uSource;
    uniform vec2 texelSize;
    uniform vec2 dyeTexelSize;
    uniform float dt;
    uniform float dissipation;
    vec4 bilerp (sampler2D sam, vec2 uv, vec2 tsize) {
        vec2 st = uv / tsize - 0.5;
        vec2 iuv = floor(st);
        vec2 fuv = fract(st);
        vec4 a = texture2D(sam, (iuv + vec2(0.5, 0.5)) * tsize);
        vec4 b = texture2D(sam, (iuv + vec2(1.5, 0.5)) * tsize);
        vec4 c = texture2D(sam, (iuv + vec2(0.5, 1.5)) * tsize);
        vec4 d = texture2D(sam, (iuv + vec2(1.5, 1.5)) * tsize);
        return mix(mix(a, b, fuv.x), mix(c, d, fuv.x), fuv.y);
    }
    void main () {
    #ifdef MANUAL_FILTERING
        vec2 coord = vUv - dt * bilerp(uVelocity, vUv, texelSize).xy * texelSize;
        vec4 result = bilerp(uSource, coord, dyeTexelSize);
    #else
        vec2 coord = vUv - dt * texture2D(uVelocity, vUv).xy * texelSize;
        vec4 result = texture2D(uSource, coord);
    #endif
        float decay = 1.0 + dissipation * dt;
        gl_FragColor = result / decay;
    }`,
    ext.supportLinearFiltering ? null : ['MANUAL_FILTERING']
);

const divergenceShader = compileShader(gl.FRAGMENT_SHADER, `
    precision mediump float;
    precision mediump sampler2D;
    varying highp vec2 vUv;
    varying highp vec2 vL;
    varying highp vec2 vR;
    varying highp vec2 vT;
    varying highp vec2 vB;
    uniform sampler2D uVelocity;
    void main () {
        float L = texture2D(uVelocity, vL).x;
        float R = texture2D(uVelocity, vR).x;
        float T = texture2D(uVelocity, vT).y;
        float B = texture2D(uVelocity, vB).y;
        vec2 C = texture2D(uVelocity, vUv).xy;
        if (vL.x < 0.0) { L = -C.x; }
        if (vR.x > 1.0) { R = -C.x; }
        if (vT.y > 1.0) { T = -C.y; }
        if (vB.y < 0.0) { B = -C.y; }
        float div = 0.5 * (R - L + T - B);
        gl_FragColor = vec4(div, 0.0, 0.0, 1.0);
    }
`);

const curlShader = compileShader(gl.FRAGMENT_SHADER, `
    precision mediump float;
    precision mediump sampler2D;
    varying highp vec2 vUv;
    varying highp vec2 vL;
    varying highp vec2 vR;
    varying highp vec2 vT;
    varying highp vec2 vB;
    uniform sampler2D uVelocity;
    void main () {
        float L = texture2D(uVelocity, vL).y;
        float R = texture2D(uVelocity, vR).y;
        float T = texture2D(uVelocity, vT).x;
        float B = texture2D(uVelocity, vB).x;
        float vorticity = R - L - T + B;
        gl_FragColor = vec4(0.5 * vorticity, 0.0, 0.0, 1.0);
    }
`);

const vorticityShader = compileShader(gl.FRAGMENT_SHADER, `
    precision highp float;
    precision highp sampler2D;
    varying vec2 vUv;
    varying vec2 vL;
    varying vec2 vR;
    varying vec2 vT;
    varying vec2 vB;
    uniform sampler2D uVelocity;
    uniform sampler2D uCurl;
    uniform float curl;
    uniform float dt;
    void main () {
        float L = texture2D(uCurl, vL).x;
        float R = texture2D(uCurl, vR).x;
        float T = texture2D(uCurl, vT).x;
        float B = texture2D(uCurl, vB).x;
        float C = texture2D(uCurl, vUv).x;
        vec2 force = 0.5 * vec2(abs(T) - abs(B), abs(R) - abs(L));
        force /= length(force) + 0.0001;
        force *= curl * C;
        force.y *= -1.0;
        vec2 vel = texture2D(uVelocity, vUv).xy;
        gl_FragColor = vec4(vel + force * dt, 0.0, 1.0);
    }
`);

const pressureShader = compileShader(gl.FRAGMENT_SHADER, `
    precision mediump float;
    precision mediump sampler2D;
    varying highp vec2 vUv;
    varying highp vec2 vL;
    varying highp vec2 vR;
    varying highp vec2 vT;
    varying highp vec2 vB;
    uniform sampler2D uPressure;
    uniform sampler2D uDivergence;
    void main () {
        float L = texture2D(uPressure, vL).x;
        float R = texture2D(uPressure, vR).x;
        float T = texture2D(uPressure, vT).x;
        float B = texture2D(uPressure, vB).x;
        float C = texture2D(uPressure, vUv).x;
        float divergence = texture2D(uDivergence, vUv).x;
        float pressure = (L + R + B + T - divergence) * 0.25;
        gl_FragColor = vec4(pressure, 0.0, 0.0, 1.0);
    }
`);

const gradientSubtractShader = compileShader(gl.FRAGMENT_SHADER, `
    precision mediump float;
    precision mediump sampler2D;
    varying highp vec2 vUv;
    varying highp vec2 vL;
    varying highp vec2 vR;
    varying highp vec2 vT;
    varying highp vec2 vB;
    uniform sampler2D uPressure;
    uniform sampler2D uVelocity;
    void main () {
        float L = texture2D(uPressure, vL).x;
        float R = texture2D(uPressure, vR).x;
        float T = texture2D(uPressure, vT).x;
        float B = texture2D(uPressure, vB).x;
        vec2 velocity = texture2D(uVelocity, vUv).xy;
        velocity.xy -= vec2(R - L, T - B);
        gl_FragColor = vec4(velocity, 0.0, 1.0);
    }
`);

const blit = (() => {
    gl.bindBuffer(gl.ARRAY_BUFFER, gl.createBuffer());
    gl.bufferData(gl.ARRAY_BUFFER, new Float32Array([-1, -1, -1, 1, 1, 1, 1, -1]), gl.STATIC_DRAW);
    gl.bindBuffer(gl.ELEMENT_ARRAY_BUFFER, gl.createBuffer());
    gl.bufferData(gl.ELEMENT_ARRAY_BUFFER, new Uint16Array([0, 1, 2, 0, 2, 3]), gl.STATIC_DRAW);
    gl.vertexAttribPointer(0, 2, gl.FLOAT, false, 0, 0);
    gl.enableVertexAttribArray(0);

    return (destination) => {
        gl.bindFramebuffer(gl.FRAMEBUFFER, destination);
        gl.drawElements(gl.TRIANGLES, 6, gl.UNSIGNED_SHORT, 0);
    }
})();

let dye;
let velocity;
let divergence;
let curl;
let pressure;
let bloom;

let ditheringTexture = createTextureAsync('');

const copyProgram = new GLProgram(baseVertexShader, copyShader);
const clearProgram = new GLProgram(baseVertexShader, clearShader);
const colorProgram = new GLProgram(baseVertexShader, colorShader);
const checkerboardProgram = new GLProgram(baseVertexShader, checkerboardShader);
const displayProgram = new GLProgram(baseVertexShader, displayShader);
const displayBloomProgram = new GLProgram(baseVertexShader, displayBloomShader);
const displayShadingProgram = new GLProgram(baseVertexShader, displayShadingShader);
const displayBloomShadingProgram = new GLProgram(baseVertexShader, displayBloomShadingShader);
const bloomPrefilterProgram = new GLProgram(baseVertexShader, bloomPrefilterShader);
const bloomBlurProgram = new GLProgram(baseVertexShader, bloomBlurShader);
const bloomFinalProgram = new GLProgram(baseVertexShader, bloomFinalShader);
const splatProgram = new GLProgram(baseVertexShader, splatShader);
const advectionProgram = new GLProgram(baseVertexShader, advectionShader);
const divergenceProgram = new GLProgram(baseVertexShader, divergenceShader);
const curlProgram = new GLProgram(baseVertexShader, curlShader);
const vorticityProgram = new GLProgram(baseVertexShader, vorticityShader);
const pressureProgram = new GLProgram(baseVertexShader, pressureShader);
const gradienSubtractProgram = new GLProgram(baseVertexShader, gradientSubtractShader);

function initFramebuffers() {
    let simRes = getResolution(config.SIM_RESOLUTION);
    let dyeRes = getResolution(config.DYE_RESOLUTION);

    const texType = ext.halfFloatTexType;
    const rgba = ext.formatRGBA;
    const rg = ext.formatRG;
    const r = ext.formatR;
    const filtering = ext.supportLinearFiltering ? gl.LINEAR : gl.NEAREST;

    if (dye == null)
        dye = createDoubleFBO(dyeRes.width, dyeRes.height, rgba.internalFormat, rgba.format, texType, filtering);
    else
        dye = resizeDoubleFBO(dye, dyeRes.width, dyeRes.height, rgba.internalFormat, rgba.format, texType, filtering);

    if (velocity == null)
        velocity = createDoubleFBO(simRes.width, simRes.height, rg.internalFormat, rg.format, texType, filtering);
    else
        velocity = resizeDoubleFBO(velocity, simRes.width, simRes.height, rg.internalFormat, rg.format, texType, filtering);

    divergence = createFBO(simRes.width, simRes.height, r.internalFormat, r.format, texType, gl.NEAREST);
    curl = createFBO(simRes.width, simRes.height, r.internalFormat, r.format, texType, gl.NEAREST);
    pressure = createDoubleFBO(simRes.width, simRes.height, r.internalFormat, r.format, texType, gl.NEAREST);

    initBloomFramebuffers();
}

function initBloomFramebuffers() {
    let res = getResolution(config.BLOOM_RESOLUTION);

    const texType = ext.halfFloatTexType;
    const rgba = ext.formatRGBA;
    const filtering = ext.supportLinearFiltering ? gl.LINEAR : gl.NEAREST;

    bloom = createFBO(res.width, res.height, rgba.internalFormat, rgba.format, texType, filtering);

    bloomFramebuffers.length = 0;
    for (let i = 0; i < config.BLOOM_ITERATIONS; i++) {
        let width = res.width >> (i + 1);
        let height = res.height >> (i + 1);

        if (width < 2 || height < 2) break;

        let fbo = createFBO(width, height, rgba.internalFormat, rgba.format, texType, filtering);
        bloomFramebuffers.push(fbo);
    }
}

function createFBO(w, h, internalFormat, format, type, param) {
    gl.activeTexture(gl.TEXTURE0);
    let texture = gl.createTexture();
    gl.bindTexture(gl.TEXTURE_2D, texture);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, param);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, param);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.CLAMP_TO_EDGE);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.CLAMP_TO_EDGE);
    gl.texImage2D(gl.TEXTURE_2D, 0, internalFormat, w, h, 0, format, type, null);

    let fbo = gl.createFramebuffer();
    gl.bindFramebuffer(gl.FRAMEBUFFER, fbo);
    gl.framebufferTexture2D(gl.FRAMEBUFFER, gl.COLOR_ATTACHMENT0, gl.TEXTURE_2D, texture, 0);
    gl.viewport(0, 0, w, h);
    gl.clear(gl.COLOR_BUFFER_BIT);

    return {
        texture,
        fbo,
        width: w,
        height: h,
        attach(id) {
            gl.activeTexture(gl.TEXTURE0 + id);
            gl.bindTexture(gl.TEXTURE_2D, texture);
            return id;
        }
    };
}

function createDoubleFBO(w, h, internalFormat, format, type, param) {
    let fbo1 = createFBO(w, h, internalFormat, format, type, param);
    let fbo2 = createFBO(w, h, internalFormat, format, type, param);

    let texelSizeX = 1.0 / w;
    let texelSizeY = 1.0 / h;

    return {
        width: w,
        height: h,
        texelSizeX,
        texelSizeY,
        get read() {
            return fbo1;
        },
        set read(value) {
            fbo1 = value;
        },
        get write() {
            return fbo2;
        },
        set write(value) {
            fbo2 = value;
        },
        swap() {
            let temp = fbo1;
            fbo1 = fbo2;
            fbo2 = temp;
        }
    }
}

function resizeFBO(target, w, h, internalFormat, format, type, param) {
    let newFBO = createFBO(w, h, internalFormat, format, type, param);
    copyProgram.bind();
    gl.uniform1i(copyProgram.uniforms.uTexture, target.attach(0));
    blit(newFBO.fbo);
    return newFBO;
}

function resizeDoubleFBO(target, w, h, internalFormat, format, type, param) {
    if (target.width == w && target.height == h)
        return target;
    target.read = resizeFBO(target.read, w, h, internalFormat, format, type, param);
    target.write = createFBO(w, h, internalFormat, format, type, param);
    target.width = w;
    target.height = h;
    target.texelSizeX = 1.0 / w;
    target.texelSizeY = 1.0 / h;
    return target;
}

function createTextureAsync(url) {
    let texture = gl.createTexture();
    gl.bindTexture(gl.TEXTURE_2D, texture);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MIN_FILTER, gl.LINEAR);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_MAG_FILTER, gl.LINEAR);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_S, gl.REPEAT);
    gl.texParameteri(gl.TEXTURE_2D, gl.TEXTURE_WRAP_T, gl.REPEAT);
    gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGB, 1, 1, 0, gl.RGB, gl.UNSIGNED_BYTE, new Uint8Array([255, 255, 255]));

    let obj = {
        texture,
        width: 1,
        height: 1,
        attach(id) {
            gl.activeTexture(gl.TEXTURE0 + id);
            gl.bindTexture(gl.TEXTURE_2D, texture);
            return id;
        }
    };

    let image = new Image();
    image.onload = () => {
        obj.width = image.width;
        obj.height = image.height;
        gl.bindTexture(gl.TEXTURE_2D, texture);
        gl.texImage2D(gl.TEXTURE_2D, 0, gl.RGB, gl.RGB, gl.UNSIGNED_BYTE, image);
    };
    image.src = url;

    return obj;
}

initFramebuffers();
multipleSplats(parseInt(Math.random() * 20) + 5);

let lastUpdateTime = Date.now();
let colorUpdateTimer = 0.0;
update();

function update() {
    const dt = calcDeltaTime();
    if (resizeCanvas())
        initFramebuffers();
    updateColors(dt);
    applyInputs();
    if (!config.PAUSED)
        step(dt);
    render(null);
    requestAnimationFrame(update);
}

function calcDeltaTime() {
    let now = Date.now();
    let dt = (now - lastUpdateTime) / 1000;
    dt = Math.min(dt, 0.016666);
    lastUpdateTime = now;
    return dt;
}

function resizeCanvas() {
    let width = scaleByPixelRatio(canvas.clientWidth);
    let height = scaleByPixelRatio(canvas.clientHeight);
    if (canvas.width != width || canvas.height != height) {
        canvas.width = width;
        canvas.height = height;
        return true;
    }
    return false;
}

function updateColors(dt) {
    if (!config.COLORFUL) return;

    colorUpdateTimer += dt * config.COLOR_UPDATE_SPEED;
    if (colorUpdateTimer >= 1) {
        colorUpdateTimer = wrap(colorUpdateTimer, 0, 1);
        pointers.forEach(p => {
            p.color = generateColor();
        });
    }
}

function applyInputs() {
    if (splatStack.length > 0)
        multipleSplats(splatStack.pop());

    pointers.forEach(p => {
        if (p.moved) {
            p.moved = false;
            splatPointer(p);
        }
    });
}

function step(dt) {
    gl.disable(gl.BLEND);
    gl.viewport(0, 0, velocity.width, velocity.height);

    curlProgram.bind();
    gl.uniform2f(curlProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
    gl.uniform1i(curlProgram.uniforms.uVelocity, velocity.read.attach(0));
    blit(curl.fbo);

    vorticityProgram.bind();
    gl.uniform2f(vorticityProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
    gl.uniform1i(vorticityProgram.uniforms.uVelocity, velocity.read.attach(0));
    gl.uniform1i(vorticityProgram.uniforms.uCurl, curl.attach(1));
    gl.uniform1f(vorticityProgram.uniforms.curl, config.CURL);
    gl.uniform1f(vorticityProgram.uniforms.dt, dt);
    blit(velocity.write.fbo);
    velocity.swap();

    divergenceProgram.bind();
    gl.uniform2f(divergenceProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
    gl.uniform1i(divergenceProgram.uniforms.uVelocity, velocity.read.attach(0));
    blit(divergence.fbo);

    clearProgram.bind();
    gl.uniform1i(clearProgram.uniforms.uTexture, pressure.read.attach(0));
    gl.uniform1f(clearProgram.uniforms.value, config.PRESSURE);
    blit(pressure.write.fbo);
    pressure.swap();

    pressureProgram.bind();
    gl.uniform2f(pressureProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
    gl.uniform1i(pressureProgram.uniforms.uDivergence, divergence.attach(0));
    for (let i = 0; i < config.PRESSURE_ITERATIONS; i++) {
        gl.uniform1i(pressureProgram.uniforms.uPressure, pressure.read.attach(1));
        blit(pressure.write.fbo);
        pressure.swap();
    }

    gradienSubtractProgram.bind();
    gl.uniform2f(gradienSubtractProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
    gl.uniform1i(gradienSubtractProgram.uniforms.uPressure, pressure.read.attach(0));
    gl.uniform1i(gradienSubtractProgram.uniforms.uVelocity, velocity.read.attach(1));
    blit(velocity.write.fbo);
    velocity.swap();

    advectionProgram.bind();
    gl.uniform2f(advectionProgram.uniforms.texelSize, velocity.texelSizeX, velocity.texelSizeY);
    if (!ext.supportLinearFiltering)
        gl.uniform2f(advectionProgram.uniforms.dyeTexelSize, velocity.texelSizeX, velocity.texelSizeY);
    let velocityId = velocity.read.attach(0);
    gl.uniform1i(advectionProgram.uniforms.uVelocity, velocityId);
    gl.uniform1i(advectionProgram.uniforms.uSource, velocityId);
    gl.uniform1f(advectionProgram.uniforms.dt, dt);
    gl.uniform1f(advectionProgram.uniforms.dissipation, config.VELOCITY_DISSIPATION);
    blit(velocity.write.fbo);
    velocity.swap();

    gl.viewport(0, 0, dye.width, dye.height);

    if (!ext.supportLinearFiltering)
        gl.uniform2f(advectionProgram.uniforms.dyeTexelSize, dye.texelSizeX, dye.texelSizeY);
    gl.uniform1i(advectionProgram.uniforms.uVelocity, velocity.read.attach(0));
    gl.uniform1i(advectionProgram.uniforms.uSource, dye.read.attach(1));
    gl.uniform1f(advectionProgram.uniforms.dissipation, config.DENSITY_DISSIPATION);
    blit(dye.write.fbo);
    dye.swap();
}

function render(target) {
    if (config.BLOOM)
        applyBloom(dye.read, bloom);

    if (target == null || !config.TRANSPARENT) {
        gl.blendFunc(gl.ONE, gl.ONE_MINUS_SRC_ALPHA);
        gl.enable(gl.BLEND);
    }
    else {
        gl.disable(gl.BLEND);
    }

    let width = target == null ? gl.drawingBufferWidth : target.width;
    let height = target == null ? gl.drawingBufferHeight : target.height;
    gl.viewport(0, 0, width, height);

    let fbo = target == null ? null : target.fbo;
    if (!config.TRANSPARENT)
        drawColor(fbo, normalizeColor(config.BACK_COLOR));
    if (target == null && config.TRANSPARENT)
        drawCheckerboard(fbo);
    drawDisplay(fbo, width, height);
}

function drawColor(fbo, color) {
    colorProgram.bind();
    gl.uniform4f(colorProgram.uniforms.color, color.r, color.g, color.b, 1);
    blit(fbo);
}

function drawCheckerboard(fbo) {
    checkerboardProgram.bind();
    gl.uniform1f(checkerboardProgram.uniforms.aspectRatio, canvas.width / canvas.height);
    blit(fbo);
}

function drawDisplay(fbo, width, height) {
    let program = pickDisplayProgram();
    program.bind();
    if (config.SHADING)
        gl.uniform2f(program.uniforms.texelSize, 1.0 / width, 1.0 / height);
    gl.uniform1i(program.uniforms.uTexture, dye.read.attach(0));
    if (config.BLOOM) {
        gl.uniform1i(program.uniforms.uBloom, bloom.attach(1));
        gl.uniform1i(program.uniforms.uDithering, ditheringTexture.attach(2));
        let scale = getTextureScale(ditheringTexture, width, height);
        gl.uniform2f(program.uniforms.ditherScale, scale.x, scale.y);
    }
    blit(fbo);
}

function pickDisplayProgram() {
    if (config.SHADING) return config.BLOOM ? displayBloomShadingProgram : displayShadingProgram;
    return config.BLOOM ? displayBloomProgram : displayProgram;
}

function applyBloom(source, destination) {
    if (bloomFramebuffers.length < 2)
        return;

    let last = destination;

    gl.disable(gl.BLEND);
    bloomPrefilterProgram.bind();
    let knee = config.BLOOM_THRESHOLD * config.BLOOM_SOFT_KNEE + 0.0001;
    let curve0 = config.BLOOM_THRESHOLD - knee;
    let curve1 = knee * 2;
    let curve2 = 0.25 / knee;
    gl.uniform3f(bloomPrefilterProgram.uniforms.curve, curve0, curve1, curve2);
    gl.uniform1f(bloomPrefilterProgram.uniforms.threshold, config.BLOOM_THRESHOLD);
    gl.uniform1i(bloomPrefilterProgram.uniforms.uTexture, source.attach(0));
    gl.viewport(0, 0, last.width, last.height);
    blit(last.fbo);

    bloomBlurProgram.bind();
    for (let i = 0; i < bloomFramebuffers.length; i++) {
        let dest = bloomFramebuffers[i];
        gl.uniform2f(bloomBlurProgram.uniforms.texelSize, 1.0 / last.width, 1.0 / last.height);
        gl.uniform1i(bloomBlurProgram.uniforms.uTexture, last.attach(0));
        gl.viewport(0, 0, dest.width, dest.height);
        blit(dest.fbo);
        last = dest;
    }

    gl.blendFunc(gl.ONE, gl.ONE);
    gl.enable(gl.BLEND);

    for (let i = bloomFramebuffers.length - 2; i >= 0; i--) {
        let baseTex = bloomFramebuffers[i];
        gl.uniform2f(bloomBlurProgram.uniforms.texelSize, 1.0 / last.width, 1.0 / last.height);
        gl.uniform1i(bloomBlurProgram.uniforms.uTexture, last.attach(0));
        gl.viewport(0, 0, baseTex.width, baseTex.height);
        blit(baseTex.fbo);
        last = baseTex;
    }

    gl.disable(gl.BLEND);
    bloomFinalProgram.bind();
    gl.uniform2f(bloomFinalProgram.uniforms.texelSize, 1.0 / last.width, 1.0 / last.height);
    gl.uniform1i(bloomFinalProgram.uniforms.uTexture, last.attach(0));
    gl.uniform1f(bloomFinalProgram.uniforms.intensity, config.BLOOM_INTENSITY);
    gl.viewport(0, 0, destination.width, destination.height);
    blit(destination.fbo);
}

function splatPointer(pointer) {
    let dx = pointer.deltaX * config.SPLAT_FORCE;
    let dy = pointer.deltaY * config.SPLAT_FORCE;
    splat(pointer.texcoordX, pointer.texcoordY, dx, dy, pointer.color);
}

function multipleSplats(amount) {
    for (let i = 0; i < amount; i++) {
        const color = generateColor();
        color.r *= 10.0;
        color.g *= 10.0;
        color.b *= 10.0;
        const x = Math.random();
        const y = Math.random();
        const dx = 1000 * (Math.random() - 0.5);
        const dy = 1000 * (Math.random() - 0.5);
        splat(x, y, dx, dy, color);
    }
}

function splat(x, y, dx, dy, color) {
    gl.viewport(0, 0, velocity.width, velocity.height);
    splatProgram.bind();
    gl.uniform1i(splatProgram.uniforms.uTarget, velocity.read.attach(0));
    gl.uniform1f(splatProgram.uniforms.aspectRatio, canvas.width / canvas.height);
    gl.uniform2f(splatProgram.uniforms.point, x, y);
    gl.uniform3f(splatProgram.uniforms.color, dx, dy, 0.0);
    gl.uniform1f(splatProgram.uniforms.radius, correctRadius(config.SPLAT_RADIUS / 100.0));
    blit(velocity.write.fbo);
    velocity.swap();

    gl.viewport(0, 0, dye.width, dye.height);
    gl.uniform1i(splatProgram.uniforms.uTarget, dye.read.attach(0));
    gl.uniform3f(splatProgram.uniforms.color, color.r, color.g, color.b);
    blit(dye.write.fbo);
    dye.swap();
}

function correctRadius(radius) {
    let aspectRatio = canvas.width / canvas.height;
    if (aspectRatio > 1)
        radius *= aspectRatio;
    return radius;
}

canvas.addEventListener('mousedown', e => {
    let posX = scaleByPixelRatio(e.offsetX);
    let posY = scaleByPixelRatio(e.offsetY);
    updatePointerDownData(pointers[0], -1, posX, posY);
});

canvas.addEventListener('mousemove', e => {
    let posX = scaleByPixelRatio(e.offsetX);
    let posY = scaleByPixelRatio(e.offsetY);
    updatePointerMoveData(pointers[0], posX, posY);
});

window.addEventListener('mouseup', () => {
    updatePoinerUpData(pointers[0]);
});

canvas.addEventListener('touchstart', e => {
    e.preventDefault();
    const touches = e.targetTouches;
    for (let i = 0; i < touches.length; i++) {
        if (i >= pointers.length)
            pointers.push(new pointerPrototype());
        let posX = scaleByPixelRatio(touches[i].pageX);
        let posY = scaleByPixelRatio(touches[i].pageY);
        updatePointerDownData(pointers[i], touches[i].identifier, posX, posY);
    }
});

canvas.addEventListener('touchmove', e => {
    e.preventDefault();
    const touches = e.targetTouches;
    for (let i = 0; i < touches.length; i++) {
        let posX = scaleByPixelRatio(touches[i].pageX);
        let posY = scaleByPixelRatio(touches[i].pageY);
        updatePointerMoveData(pointers[i], posX, posY);
    }
}, false);

window.addEventListener('touchend', e => {
    const touches = e.changedTouches;
    for (let i = 0; i < touches.length; i++)
        for (let j = 0; j < pointers.length; j++)
            if (touches[i].identifier == pointers[j].id)
                updatePoinerUpData(pointers[j]);
});

window.addEventListener('keydown', e => {
    if (e.code === 'KeyP')
        config.PAUSED = !config.PAUSED;
    if (e.key === ' ')
        splatStack.push(parseInt(Math.random() * 20) + 5);
});

function updatePointerDownData(pointer, id, posX, posY) {
    pointer.id = id;
    pointer.down = true;
    pointer.moved = false;
    pointer.texcoordX = posX / canvas.width;
    pointer.texcoordY = 1.0 - posY / canvas.height;
    pointer.prevTexcoordX = pointer.texcoordX;
    pointer.prevTexcoordY = pointer.texcoordY;
    pointer.deltaX = 0;
    pointer.deltaY = 0;
    pointer.color = generateColor();
}

function updatePointerMoveData(pointer, posX, posY) {
    pointer.moved = pointer.down;
    pointer.down = true;
    pointer.prevTexcoordX = pointer.texcoordX;
    pointer.prevTexcoordY = pointer.texcoordY;
    pointer.texcoordX = posX / canvas.width;
    pointer.texcoordY = 1.0 - posY / canvas.height;
    pointer.deltaX = correctDeltaX(pointer.texcoordX - pointer.prevTexcoordX);
    pointer.deltaY = correctDeltaY(pointer.texcoordY - pointer.prevTexcoordY);
}

function updatePoinerUpData(pointer) {
    pointer.down = false;
}

function correctDeltaX(delta) {
    let aspectRatio = canvas.width / canvas.height;
    if (aspectRatio < 1) delta *= aspectRatio;
    return delta;
}

function correctDeltaY(delta) {
    let aspectRatio = canvas.width / canvas.height;
    if (aspectRatio > 1) delta /= aspectRatio;
    return delta;
}

function generateColor() {
    let c = HSVtoRGB(Math.random(), 1.0, 1.0);
    c.r *= 0.15;
    c.g *= 0.15;
    c.b *= 0.15;
    return c;
}

function HSVtoRGB(h, s, v) {
    let r, g, b, i, f, p, q, t;
    i = Math.floor(h * 6);
    f = h * 6 - i;
    p = v * (1 - s);
    q = v * (1 - f * s);
    t = v * (1 - (1 - f) * s);

    switch (i % 6) {
        case 0: r = v, g = t, b = p; break;
        case 1: r = q, g = v, b = p; break;
        case 2: r = p, g = v, b = t; break;
        case 3: r = p, g = q, b = v; break;
        case 4: r = t, g = p, b = v; break;
        case 5: r = v, g = p, b = q; break;
    }

    return {
        r,
        g,
        b
    };
}

function normalizeColor(input) {
    let output = {
        r: input.r / 255,
        g: input.g / 255,
        b: input.b / 255
    };
    return output;
}

function wrap(value, min, max) {
    let range = max - min;
    if (range == 0) return min;
    return (value - min) % range + min;
}

function getResolution(resolution) {
    let aspectRatio = gl.drawingBufferWidth / gl.drawingBufferHeight;
    if (aspectRatio < 1)
        aspectRatio = 1.0 / aspectRatio;

    let min = Math.round(resolution);
    let max = Math.round(resolution * aspectRatio);

    if (gl.drawingBufferWidth > gl.drawingBufferHeight)
        return { width: max, height: min };
    else
        return { width: min, height: max };
}

function getTextureScale(texture, width, height) {
    return {
        x: width / texture.width,
        y: height / texture.height
    };
}

function scaleByPixelRatio(input) {
    let pixelRatio = window.devicePixelRatio || 1;
    return Math.floor(input * pixelRatio);
}